Electrolytic material removal apparatus



Nov. 5, 1968 J. D. ANDREWS ET AL 3,409,534

ELECTROLYTIC MATERIAL REMOVAL APPARATUS Filed Dec. 29, 19 Q 2 sheets-sheet l I I H 5150240 I I /d 744/15 INVENTOR5. JflA/ij 0. 44 025146 BY (46.4 4-. ai /#873 Nov. 5, 1968 J, ANDREWS ETAL 3,409,534

ELECTROLYTIC MATERIAL REMOVAL APPARATUS Filed Dec. 29, 1965 2 Sheets-Sheet 2 INVENTORJ.

United States Patent Office 3,409,534 Patented Nov. 5, 1968 3,409,534 ELECTROLYTIC MATERIAL REMOVAL APPARATUS James D. Andrews, Cincinnati, and Carl E. Shurts, Loveland, Ohio, assignors to General Electric Company, a

corporation of New York Filed Dec. 29, 1965, Ser. No. 517,239 3 Claims. (Cl. 204-224) ABSTRACT OF THE DISCLOSURE An improved apparatus for electrolytically producing cavities in a conductive workpiece is described. A cathode is located within a hollow electrolyte directing nozzle in a particular manner so as to provide process control, as well as accurate and repeatable cavities within the workpiece.

The invention described and claimed herein resulted from work done under United States Government contract FA-SS-64-1. The United States Government has an irrevocable, non-exclusive licenseunder this United States patent application to practice and have practiced the invention claimed herein, including the unlimited right to sublicense others to practice and have practiced the invention claimed in this United States patent application for any purposes whatsoever.

This invention relates to the electrolytic removal of material from an electrically conductive workpiece and, more particularly, to apparatus for use in the production of multiple small holes or cavities in a workpiece by such a method.

In general, the method for removing material electrolytically from an electrically conductive workpiece in cludes placing a cathode-tool and an anode-workpiece one opposite the other while at the same time passing an electric current between the cathode and anode through an electrolyte. The shape and size of the cathode depends upon the shape and size of that portion of the workpiece which is to be removed and the cavity or hole to be produced. This process and its associated apparatus and tooling has been described in detail in the public literature and in the patented art. The known literature is directed principally to the use of relatively large cathodes the shape of which is closely related to the shape to be produced in the workpiece. Such cathodes are positioned across a relatively narrow gap from the workpiece. This method, which is sometimes referred to as electrolytic machining, electrolytic cutting, electrolytic drilling, and the like, has been described to include passing current at relatively low voltages between the cathode and the anodeworkpiece.

In co-pending application Ser. No. 474,833, filed July 26, 1965, and assigned to the assignee of the present invention, an improved electrolytic material removal method and apparatus is described. In that method, a stream or jet of charged electrolyte is directed from an electrolyte directing means, such as a nozzle, toward a workpiece with the actual cathode spaced at a relatively greater distance from the workpiece than was previously allowable in other types of electrolytic material removal methods. That invention describes the unusual advantage in maintaining the power input to the charged electrolyte stream between the cathode and the workpiece at a level which produces in that electrolyte stream a condition at least at the threshold of glow discharge. Prior to that invention, the diameter of holes which could be produced electrolytically in an electrically conductive workpiece was limited by the size of a cathode tube through which electrolyte could pass and which could penetrate the workpiece. Generally a practical limitation on the tube outside diameter for production use was no less than about 0.050. Through the use of the method and apparatus of the above identified co-pending application, a hole could be produced having a diameter of as little as 0.001 because the actual cathode was not required to penetrate the workpiece.

For the production of single holes or single narrow cavities in a workpiece, a single electrolyte nozzle could be readily located opposite a workpiece. Then either the workpiece or the nozzle could be fed one toward the other or could be traversed relatively one to the other to produce a desired shape or cavity. However, in the production of a plurality of holes or cavities located at specific and closely positioned points on a workpiece surface, the co-ordinated movement of the plurality of electrolyte di recting nozzles and workpiece presented operational difficulties. This was a particular problem in those situations in which it was desired that the multiple separate cathodes, and hence the electrolyte nozzles, be fed toward the workpiece. Such an embodiment required movement of the means to carry electrolyte to each of the electrolyte directing nozzles from a single source of electrolyte as well as movement of the means to charge each of the electrolyte streams from a single source of electrical power.

A principal object of the present invention is to provide improved apparatus for use in the electrolytic removal of material from an electrically conductive workpiece through a plurality of charged electrolyte streams each at least at the threshold of glow discharge and each directed from nozzles readily movable with respect to the workpiece.

Another object is to provide such apparatus which allows easy replacement of nozzles such as for change in hole size or because of nozzle damage.

A further object is to provide improved apparatus for use in such an electrolytic material removal process in which the cathode is particularly located with respect to the workpiece to provide process control as well as accurate and repeatable hole production.

These and other objects and advantages will be more easily recognized from the following detailed description, examples and from the drawing in which:

FIG. 1 is a partially sectional, partially diagrammatic view of one form of the apparatus of the present invention; and

FIG. 2 is a partially sectional view of another form of the electrolyte manifold in the apparatus of the present invention.

The above objects were achieved according to the present invention by providing improved apparatus in which the electrolyte and an electric conducting means, electrically connected with a source of electrical power, are brought together in an electrolyte chamber of a manifold. Those surfaces of the manifold which are'in contact with the electrolyte are a dielectric material. In one practical form, the manifold is made of a dielectric material. The manifold includes means to introduce the electrolyte into the electrolyte chamber. The electrical conducting means in the electrolyte chamber is electrically connected with an electric power source. Communicating with the manifold are a plurality of hollow flexible electrolyte conduits of a dielectric material, such as a plastic. Each conduit, such as a tube, communicates with the electrolyte chamber to allow the electrolyte to pass from the chamber into the conduit. A flexible cathode which is electrically connected with the electric conducting means passes through each conduit and terminates in a cathode tip beyond that end of the conduit remote from the manifold. The apparatus further includes a plurality of hollow electrolyte directing nozzles of a dielectric material comprising a body, a capillary end open at the nozzle tip and a transition section joining thebody with the capillary end. The transition section decreases in diameter from the body toward the capillary end. There are means to connect that end of each conduit, remote from the manifold, with its respective electrolyte directing nozzle to allow the electrolyte to flow through each nozzle and toward a workpiece from teh nozzle tip. Thus the cathode tip is located within the body of the nozzle. It has been found that the cathode tip must be located at a point about %%t" from the location at which the transition section joins the body of the nozzle. The apparatus further includes nozzle holding and locating means releasably connected with the body of each nozzle to hold and position the nozzles with respect to the workpiece.

One embodiment of the present invention is shown in the partially sectional, partially diagrammatic FIG. 1. Manifold in this embodiment is made of a dielectric material such as a polymerized methyl methacrylate resin some forms of which are known as Lucite plastic and Plexiglas plastic. Within manifold 10 is an electrolyte chamber 12 into which electrolyte from reservoir 14 is fed by pump 16 through an opening 18. An electrical conducting means 20, such as a wire or rod, is connected electrically through a wall such as at 22 of the manifold to a source of electrical power not shown but represented by the negative charge 24. Because the electrolyte in electrolyte chamber 12 can be electrically charged by electrical conductor 20, the walls of the manifold 10 in contact with the electrolyte in chamber 12 are covered with a dielectric material in the event the entire body of the manifold 10 is not itself of a dielectric material.

As shown in the embodiment of FIG. 1, each of a plurality of hollow flexible electrolyte conduits 26, such as of plastic tubing, is connected to manifold 10 so that each communicates with the electrolyte chamber 12 to allow electrolyte to pass from the chamber into each conduit. Conduits 26, electrolyte supply means such as tube 28, and electrical conductor 20 through wall 22 can be secured to the manifold by a clamping and sealing means 30, for example, of a type shown in more detail in FIG. 2.

In electrical connection with electric conductor 20 are a plurality of flexible cathodes such as wires 32 each extending through an electrolyte conduit 26 and extending past end 34 of each conduit 32, remote from manifold 10. Each cathode terminates in cathode tip 36. Each hollow electrolyte directing nozzle, one of which is shown generally at 40, includes a body 42 and a capillary end 44 open at tip 46 which is directed toward workpiece 48. Between capillary end 44 and body 42 is a transition section 50 joining the body 42 with the capillary end 44 and decreasing in cross-sectional diameter from the body toward the capillary end. The location 52 at which the transition section joins the body of the nozzle is that at which the transition section starts to decrease in cross-sectional diameter with respect to the cross-sectional diameter of the body.

It has been found that cathode tip 36 must be located within a distance, shown as D in the drawing, of about A" to from location 52 at which the transition section joins the body of the nozzle. If tip 36 is closer to location 52 than about A", the flow of electrolyte through capillary end 44 is reduced to a point which causes loss of control of hole size produced in workpiece 48, the production generally larger than desired holes and significantly reduced life of nozzle tip 46. If cathode tip 36 is farther than about A from location 52 gases in the electrolyte form into bubbles which results in loss of process control and erratic hole size. This distance is particularly significant with the use of capillary ends having an inside diameter of about 0.03 or less.

The body of each nozzle 40 is releasably secured by clamping means such as 54 to its respective conduit 26 to allow the electrolyte to pass from the conduit into the nozzle and subsequently to workpiece 48. The body of each nozzle 40 is releasably secured with a nozzle holding and locating means such as metal plate 56 through which holes such as 58 have been produced to receive the body of nozzle 40. The holes 58 are large enough to allow nozzle 40 to be removed for replacement by release or removal of the clamping means securing the nozzle with the conduit 26 and with means 56. In order to locate nozzle tip 46, and indirectly cathode tip 36, with respect to workpiece 48 or with respect to other of the plurality of nozzles, a locator 60 and a lock means 62 are attached with body 40. When it is desired to remove nozzle 40 either to replace it with a different size nozzle or because nozzle 40 has become damaged, clamp means 54 and locators and locks 60 and 62, respectively, can be removed and the nozzle can be replaced without disturbing the means connected with manifold 10 to supply electrolyte to each conduit 26 and without disturbing the electrical connection between the power source 24, electric conductor 20 and the plurality of cathodes 32.

As shown in FIG. 1 a plurality of cathode wires 32 are connected with electrical conductor 20 at a plurality of points 62. However, it will be understood that points 62 can be a common point as well as separate points on conductor 20. The embodiment of FIG. 2 shows a manifold on which point 62 is a common one for each of the cathodes 32.

The nozzle holding and locating means 56 of FIG. 1 can be movable such as with standard and well known machines, represented diagrammatically by arrows 64, in a variety of directions with respect to workpiece 48. The advantage of providing means 56 and hence nozzles 40 to be movable in a variety of directions with respect to the workpiece while at the same time maintaining manifold 10 in a fixed position has particular significance in the production of the plurality of holes or cavities in workpiece 48. In addition to the more simple arrangement of components, problems relating to the loosening of connectors, wear and breakdown of insulation and contacts, and the like with regard to manifold 10 are thus eliminated. At the same time easy replacement of nozzles 40 are provided.

In FIG. 2, the manifold is shown in an embodiment generally at 10a in which a plurality of channels 70, functionally equivalent to openings 72 in the manifold 10 of FIG. 1, are directed to a common point. Cathodes 32 are joined with electrical conductor 20 at 62. Electrolyte from conduit 28 is directed to that point for passage subsequently through each channel 70 to flexible conduit 26 as described above. By using a plurality of manifolds 10a of the type shown in FIG. 2 with a'single nozzle holding and locating means such as 56 shown in FIG. 1, the arrangement of the plurality of conduits 26 to the electrolyte nozzles 40 can be made more readily accessible.

The following examples will more clearly describe the specific conditions and the specific effects of the positioning of cathode tip 36 in the body 42 of nozzle 40 at a dis- .tance between about MU' A" from the start 52 of transition section 50.

Example 1 A nozzle having a capillary end of 0.014 outside diameter and 0.0125" inside diameter was used in an electrolyic process to produce holes in a tube of a nickel base alloy having a nominal composition, by weight, of 0.1% (max.) C; 15% Cr; 3% Cb; 3% Mo; 3% W; 7% Fe; 0.5% A1; 0.6% Ti; 0.006 B; with the balance Ni and incidental impurities, and sometimes referred to as IN 102 nickel base alloy. The tube had an outside diameter of about 0.2" and a wall thickness of about 0.04". The aim was to produce 0.017" diameter holes.

The electrolyte used was an aqueous solution of 10% H 50 applied at a pressure of about 40-60 p.s.i. The power applied was at a potential of 500 volts at 300 milliamps.

In this example, the tip 36 of cathode 32 was placed within the range of A" to A" from the location 52 at which the transition section of the nozzle joins the nozzle body. Holes of 0.017" were consistently produced and nozzle tip 46 was essentially unaffected for as many as about 10,000 holes.

Example 2 The conditions, materials and apparatus of Example 1 were used in this example except that tip 36 of cathode 32 was placed at a distance less than A" from location 52. Holes of about 0.020" diameter were produced rather than 0.017" and the life of nozzle tip 46 was limited to about 100 holes before replacement was required.

. Example 3 The conditions, materials and apparatus of Example 1 were used in this example except that tip 36 of cathode 32 was placed at a distance greater than A from location 52. Holes of erratic size fluctuating between 0.015 and 0.017" were produced along with formation of gas bubbles which aflected process control.

Thus through the practice of the present invention in. eluding the particular placement of cathode tip 36 within nozzle 40, unusual repeatability and accuracy in hole production can be achieved in an electrolytic material removal process involving a jet of charged electrolyte.

Although the present invention has been described in connection with particular examples and embodiments, it will be understood by those skilled in the art the variations and modifications of which the invention is capable. It is intended to include in the appended claims all such variations and modifications.

What is claimed is:

1. Improved apparatus for use in the electrolytic removal of material from an electrically conductive workpiece comprising:

a manifold having walls enclosing an electrolyte chamher, the surfaces of the manifold in contact with the electrolyte being dielectric;

means to introduce electrolyte into the chamber;

an electric power source;

electric conducting means in the electrolyte chamber electrically connected with the electric power source;

a hollow flexible electrolyte conduit of a dielectric material communicating with the electrolyte chamber to allow electrolyte to pass from the chamber into the conduit;

a flexible cathode electrically connected with the electric conducting means, the cathode passing through the conduit and terminating in a cathode tip beyond an end of the conduit remote from the manifold;

a hollow electrolyte directing nozzle of a dielectric material comprising a body, a capillary end open at the nozzle tip and a transition section joining the body with the capillary end, the transition section decreasing in diameter from a location on the body toward the capillary end, the nozzle tip directed at the electrically conductive workpiece;

means connecting the conduit with the nozzle to allow electrolyte to flow from the conduit through the nozzle and toward the workpiece from the nozzle tip;

the cathode tip being located 'Within the body of the nozzle about A"% from the location at which the transition section joins the body of the nozzle; and

nozzle holding and locating means releasably connected with the body of the nozzle to hold and to position the nozzle with respect to the workpiece.

2. The improved apparatus of claim 1 for use in the electrolytic removal of material from an electrically conductive workpiece, comprising:

a manifold of a dielectric material having walls enclosing an electrolyte chamber;

means to introduce electrolyte under pressure into the chamber;

an electric power source at a potential of at least 300 volts;

electric conducting means in the elestrolyte chamber passing through a wall of the manifold and electrically connected with the electric power source;

a plurality of hollow flexible electrolyte conduits each of a dielectric material and each communicating with the electrolyte chamber to allow electrolyte to pass from the chamber into each conduit;

a flexible cathode for each conduit electrically connected with the electric conducting means, each cathode passing from the electrolyte chamber through the conduit and terminating in a cathode tip beyond an end of the conduit remote from the manifold;

a hollow electrolyte directing nozzle for each cathode of a dielectric material comprising a body, a capillary end open at the nozzle tip and a transition section joining the body with the capillary end, the capillary end having an inside diameter of no greater than about 0.03", the transition section decreasing in diameter from a location on the body toward the capilllary end, the open nozzle tip directed toward the electrically conductive workpiece;

releasable means connecting each conduit with its associated nozzle to allow electrolyte to flow from the conduit through the nozzle and toward the workpiece from the nozzle tip;

the cathode tip being located within the body of the nozzle about A-%" from the location at which the transition section joins the body of the nozzle; and

movable nozzle holding and locating means releasably connected with the body of the nozzle to hold and to position the nozzle with respect to the workpiece.

3. The improved apparatus of claim 2 for use in the electrolytic removal of material from an electrically conductive workpiece comprising:

a plurality of manifolds of a dielectric material, each having Walls enclosing an electrolyte chamber;

means to introduce electrolyte under pressure into each of the electrolyte chambers;

an electric power source at a potential of at least 300 volts;

electric conducting means in each electrolyte chamber passing through a wall of each manifold, each electric conducting means electrically connected with the electric power source;

a plurality of hollow flexible electrolyte conduits each of a dielectric material, each communicating with its respective electrolyte chamber to allow electrolyte to pass from the chamber into each conduit;

a flexible cathode for each conduit electrically connected with the electric conducting means in its respective electrolyte chamber, each cathode passing from its electrolyte chamber through the conduit and terminating in a cathode tip beyond an end of the conduit remote from the manifold;

a hollow electrolyte directing nozzle for each cathode of a dielectric material comprising a body, a capillary end open at the nozzle tip and a transition section joining the body with the capillary end, the capillary end having an inside diameter of no greater than about 0.03", the transition section decreasing in diameter from the body toward the capillary end, the open nozzle tip directed toward the electrically conductive workpiece;

releasable means connecting each conduit with its associated nozzle to allow electrolyte to flow from the conduit through the nozzle and toward the workpiece from the nozzle tip;

the cathode tip being located within the body of the nozzle about MH A" from the location at which the transition section joins the body of the nozzle; and

movable nozzle holding and locating means releasably connected with the body of the nozzle to hold and to position the nozzle with respect to the workpiece.

(References on following page) References Cited UNITED STATES PATENTS Bailey.

Evers 204224 XR 5 Vaughn.

Andrews 204224 8 OTHER REFERENCES A. Uhlir, Jr.: Micromachining With Virtual Electrodes, The Review of Scientific Instruments, vol. 26, No. 10, October 1955.

HOWARD S. WILLIAMS, Primary Examiner.

D. R. VALENTINE, Assistant Examiner. 

